Proc Natl Acad Sci U S A
April 1, 1991;
Expression of a mRNA related to c-rel and dorsal in early Xenopus laevis embryos.
We describe a Xenopus mRNA, Xrel1
, that is related to the avian protooncogene c-rel
, the embryonic pattern gene dorsal of Drosophila, and the mammalian transcription factor NK-kappa B/KBF1
. The sequence of Xrel1
is homologous to the other rel
-related proteins in the large amino-terminal region that defines this class of transcriptional regulators, but the carboxyl-terminal part of the protein is quite different. Xrel1
mRNA is present throughout oogenesis and during early embryogenesis at 4 x 10(5) transcripts per oocyte
transcripts are present in all of the dissected parts of early embryos that we have examined. They are enriched in the animal hemisphere
compared to the vegetal hemisphere
of oocytes and blastulae.
Proc Natl Acad Sci U S A
[+] show captions
FIG. 1. (A) cDNA sequence of Xrell. The poly(A) addition signal is boxed and the stop codon is denoted by an asterisk. The region of
homology to the other members of the rel family is underlined. (B) Comparison of the predicted protein sequence of Xrell with those of other
members of the rel family. The Xrell sequence was aligned with those of rel-related sequences from turkey (c-rel; ref. 4), mouse (mc-rel; ref.
7), human (hc-rel; ref. 8), Drosophila dorsal (12), and NF-KB (9), in a region spanning the amino-terminal domain of conservation (amino acids
18-305 of Xrell). Identical and conservatively substituted amino acid residues are shown in boldface type.
FIG. 2. Northern blot analyses of developmental expression of
Xrell. (A) Accumulation of Xrell transcripts during oogenesis.
RNA from five oocytes was loaded per lane. Ethidium bromide
staining of the 18S rRNA shows the accumulation of total RNA with
increasing size of oocyte. The time in months is the approximate
time oogonia take to reach each oocyte stage. kb, Kilobases. (B)
Accumulation of Xrell transcripts during embryogenesis. RNA
from five embryos was loaded per lane. Approximately equal
amounts of total RNA were loaded as shown by ethidium bromide
staining of 18S rRNA.
FIG. 3. Distribution of Xrell transcripts in early development. In A, 6 animal and 6 vegetal hemispheres of unfertilized eggs, in B, 15 animal, 10
equatorial, 25 vegetal pieces, and three whole embryos of mid-blastulae, and in C, 20-50 neurula trunk parts, six anterior, six middle, and six posterior
parts, and three whole embryos of late neurulae were analyzed by RNase protection for Xrell and 5S rRNA transcripts. Any differences in the
concentration ofXrell transcripts in the various fractions are not more than a fewfold. The neural tube, which, in the assay shown, appears to contain
very little Xrell RNA, did not reproducibly have a lower concentration than in the other tissues. Yeast tRNA (5 Ag) was used as a hybridization control
(tRNA lane). The numbers on the right hand side of this figure are the sizes in bases of the end-labeled Hinfl fragments of pBR322 used as molecular